Question 244537 in Reactjs Question posted in
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Reactjs – "React: 'Each child in a list should have a unique 'key' prop' warning in my component hierarchy"

I’m encountering a warning in my React application, and I’m seeking assistance in understanding and resolving it. The warning message states:

Warning: Each child in a list should have a unique "key" prop.

I’ve reviewed my code and made sure that I’m providing a unique key prop in my component where I’m mapping over an array, but the warning still persists. Here’s the relevant code structure:

This is the error

This is my Home.js file
This is my MealDetails.js file

I’ve confirmed that the meal._id values are unique within the meals array, and I’m using them as keys when rendering MealDetails components. However, I’m still receiving the warning.

Here are some additional details that might help diagnose the issue:

  • I’ve checked other components and haven’t found any issues with key assignment.
  • The error doesn’t seem to originate from the MealDetails component itself.
  • I’ve reviewed my context and reducer code (provided in another question), and it appears to be correctly set up.

Any insights into what might be causing this warning and how to resolve it would be greatly appreciated. Thank you!

Tags:

2

Answers


  1. 0

    You can also use the built in index argument in the map() function. More info can be found in the docs

    As a test, I would try updating your code to add the map method’s index argument and pass it in as a key prop of the top level JSX element, like so:

    {meals &&
   meals.map((meal, index) => {
   return <MealDetails meal={meal} key={index} />;
})}
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  2. 0

    You need to assign unique key value in map() of the array.
    If you have a unique key in each element of array, you can that one. But if not, you can use index of map.

    { meals.map((meal, idx) => <MealDetails meal={meal} key={idx} />) }

    or

    { meals.map(meal => <MealDetails meal={meal} key={meal._id} />) }

    But you have done. You need to check meal._ids are unique.

    { meals.map(meal => {
  console.log(meal._id);
  return <MealDetails meal={meal} key={meal._id} /> 
  })
}

    You can check the results on the console of web browser. If the same _ids are exists or _id is undefined, rewrite the meals collection.
    thanks.

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